Effects Of Application Of Mixed Chemical Fertilizer With Composts On Crop Growth And Soil Fertility In Rice-Wheat Rotation System

Rice and Wheat are the most important staple crops in the world. The sustainable production of rice-wheat crop rotation system concerns the food security of China and the world. The conservation of the soil fertility is essential for the world to maintain the food production. Combined application of organic and inorganic compound fertilizers is realized as a fertilization mold with high nutrient use efficiency and high yield. However, few studies have been reported on effects of mass-produced complex fertilizers made from chemical fertilizers and compost on plant growth and soil fertility. Field experiments were carried out in a rice-wheat rotation system for4years to study the effects of application of the mass-produced complex fertilizer made from chemical fertilizers and pig manure compost on crop yields, biomass and nitrogen uptake and soil properties such as available nitrogen contents, soil microbial biomass and microbial diversity, soil organic matter and soil aggregates with focus on the mechanisms of soil organic matter transformation and accumulation under different fertilization molds. The main results were listed as follows:The yields of rice obtained by the organic-inorganic compound fertilizer (OICF)(8504.2～9642.2kg·hm-2) were higher than that of chemical fertilizer treatment (CF)(7918.7～9013.3kg·hm-2) in3successive rice seasons, but the difference in yield between the two treatments was not significant. The number of spike and grains per rice panicle of OICF treatment were lower than that of CF treatment in2007, but in2008and2009the number of spike and grains per rice panicle of OICF treatment were higher than that of CF treatment. The aboveground biomass and aboveground nitrogen accumulation and available soil nitrogen of OICF treatment were lower than that of CF treatment in early stage of rice but higher than that of CF treatment in later stage of rice for all three rice season. The nitrogen utilization efficiency of rice for OICF treatments (44.0%-43.5%) was higher than that of CF treatment through three rice seasons (33.8%-36.9%).The yields of wheat of CF treatment (6760.0kg·hm-2、6900.7kg·hm-2) were higher than that of OICF treatment (4583.9kg·hm-2、6850.7kg·hm-2) in wheat season of 2006-2007and2007-2008, and the difference between the two treatments was significant in2006-2007. The yields of wheat by OICF treatment (4783.3kg-hm-2) were higher than that of CF (4674.4kg-hm-2) in2008-2009, but no significant difference existed between the two treatments. The number of spike and grains per panicle of OICF treatment were lower than that of CF treatment under wheat season in2006-2007, but higher in2008-2009. The aboveground biomass and aboveground nitrogen accumulation of OICF treatment were lower than that of CF treatment through whole stage of wheat in2006-2007, but higher than CF treatment in later stage of wheat in2007-2008and2008-2009. The soil available nitrogen of OICF treatment were lower than that of CF treatment through whole stage of wheat in2006-2007, but higher than that of CF treatment in later stage of wheat in2007-2008and2008-2009. The nitrogen utilization efficiency of wheat under OICF treatment (27.3%) was lower than that of CF treatment (33.7%) in2006-2007, but in2007-2008and2008-2009the nitrogen utilization efficiency of wheat under OICF treatment (36.5%,45.8%) was higher than that of CF treatment (34.5%,35.8%).To understand the mechanism of increasing crop grain through the aspect of soil fertility, the soil was sampled in the maturity of wheat and rice to study the soil organic matter, aggregation and microbial properties. The results were listed as follows:The content of soil organic carbon (SOC)(16.9g-kg-119.8g-kg-1)and soil total nitrogen (TN)(1.93g-kg、2.15g·kg-1) and the mean weight diameter (MWD) of soil aggregates under OICF treatment (1.1mm) and pig manure compost fertilizer (PMC) treatment (1.9mm) were higher than that of CF treatment (1.0mm) in wheat season, and the difference between CF and PMC treatments were significant. The content of SOC and TN in macro-aggregates (>0.25mm) under OICF treatment and PMC treatment were higher than that of CF treatment in wheat season, and the difference between CF and PMC treatments were significant. The content of SOC (14.9g·kg-1、17.7g·kg-1) and TN (1.87g·kg-1、2.13g·kg-1) under OICF treatment and PMC treatment were higher than that of CF treatment (14.6g·kg-1、1.82g·kg-1) in rice season, and the difference between CF and PMC treatments were significant. The effect of different fertilizer on soil aggregate stability in rice season was little. The content of SOC and TN in all aggregate fractions under OICF treatment and PMC treatment were higher than that of CF treatment in rice season, and the difference between CF and PMC treatments were significant.After analyzing the chemical structure of soil organic matter through CPMAS13C NMR, we find that different fertilizer have different influences on the chemical structure of organic matter in bulk soil and aggregates. In the soil of wheat season, the relative content of alkyl C of OICF treatment (23.43%) and PMC treatment (24.58%) were lower than that of CF treatment (24.61%), the relative content of O-alkyl C of the both were higher than that of CF treatment, and ratio of Alkyl C/O-alkyl C (0.50.0.51) were all lower that of CF treatment (0.56). In the soil of rice season, the influences of various fertilizer treatments on the chemical structure of soil organic matter were different from that of wheat season. The relative content of alkyl C of OICF treatment (30.57%)was higher than that of CF treatment (28.22%), while the relative content of O-alkyl C were all lower than that of CF treatment, and the relative content of alkyl C and O-alkyl C of PMC treatment were all lower than that of CF treatment. Besides, the chemical structures of soil organic matter among different size aggregates were also different, and the different fertilization treatments had a great impact on the chemical structure of organic matter in macro-aggregates. The relative content of O-alkyl C in macro-aggregate of PMC treatment were higher than that of other treatments, and the relative content of alkyl C in macro-aggregate of PMC treatment were lower than that of other treatments, which contributed to lower decomposition extent of SOM in macro-aggregate under PMC treatment.The different fertilization treatment had a great impact on the density fraction of SOM. The content of free light fraction and occlude light fraction under OICF and PMC treatment were higher than that of CF treatment, and the content of heavy fraction of free light fraction and occlude light fraction under OICF and PMC treatment were lower than that of CF treatment for both season.The effect of different fertilizer on soil microbe quantities and soil microbial diversity were studied through PCR-DGGE and real-time PCR. The soil microbial biomass C (275.82mg kg-1) of OICF and PMC treatments (278.63mg kg-1)were higher than CF treatment (267.63mg kg"1.250.14mg kg-1) for wheat and rice season, and the difference between PMC and CF treatment was significant. The soil microbial diversity of OICF and PMC treatments were better than that of CF treatment in the wheat and rice seasons. The number of soil bacterial16S rRNA copies and soil fungal18S rRNA copies in OICF and PMC treatments were higher than that of CF treatment in wheat and rice season, and the difference between PMC and CF treatment was significant.In conclusion, compared with the chemical fertilizer, using organic and inorganic compound fertilizer can not only obtain considerable or higher crop yields, but also contribute to increasing the amount and quality of soil organic matters, improving the physical structure of soil, providing good condiction for crop growth and increasing the soil fertility and productivity.